1. Field of the Invention
The present invention relates to the marking of chips or tokens for gaming tables having the general shape of a disk, or of objects of similar shape, by pad printing, and more particularly, the holding of chips or tokens during pad-printing operations. Gambling chips, also called casino chips, should be understood to mean any element which can be used in a gambling hall, especially on the gaming tables, and representing a nominal value which may or may not be predetermined. Generally, these chips are manufactured from a rigid and scratch-resistant plastic.
2. Discussion of Background Information
Chips for a gaming table are, almost systematically, given a decoration by marking on their faces and/or sides. The decoration depends on the eventual uses of the chips and ranges from the simplest to the most complex. In particular, French patent FR 2 730 392 describes the use of pad printing for marking the surface of the faces and/or the sides of chips (as opposed to volume marking using multi-shot injection molding of variously colored plastics).
The publication WO 98/43816, describes a method of marking by pad printing making it possible to mark the faces and the perpendicular side of a chip with considerable accuracy, and relates especially to marking one face and the side of the chip simultaneously. Publication WO 98/43816 also describes a pad-printing system using a holding or placement device for the chip which has an axial support with an end face intended to carry the chip. The holding or placement device is combined with vacuum suction means operating in the steady state for keeping the chip pressed directly or indirectly on the support.
Although this type of system is generally satisfactory, it is sometimes limited when holding chips under vacuum in the more tricky cases. For example, it is not very well suited for:
pad printing on chips with “granite-like” faces provided with a relief consisting of small pyramids less than one millimeter in height;
four-color pad printing which requires the perfect and continuous centering of a chip during the four successive marking operations; or
pad printing a side which requires highly accurate axial positioning of the chip with respect to the pad.
In addition, the use of permanent vacuum suction in high-yield pad-printing systems capable of marking several chips simultaneously requires assemblies which are often complex in terms of suction lines and of powerful vacuum suction means increasing the costs of these plants.